This particular cable has the stripper in a little box close to the console side, so it would actually help with interference along the cable. Also don’t forget that some SCART switches like the popular Bandridge ones have some issues with composite video bleeding into RGB, a SCART head mounted sync stripper for my only sync-on-composite console (GC) made a real difference.
Obviously, like you said, a sync stripper makes little sense for a console that natively outputs proper csync. I can only imagine this cable was designed to provide csync on both NTSC & PAL Saturns, the latter lacking native csync.
One problem with cables from this seller seems to be that, at least for a while, he omitted the 470 ohm resistor after the sync stripper. This means this cable might be outputting a dangerous TTL-level sync signal, causing everything from incompatibility to equipment failure. You could inspect the cable (likely need to remove some hot glue in the stripper box) and/or contact the seller. I’d recommend a cable from retrogamingcables.co.uk in any case.